Now the advice I give to all would-be native app testers is that you need to know how to write a simple native app. It really helps, trust me! It helps as most of the automation tools require some familiarity with the tools used to create the app (especially the UI) and it also helps in your discussions with dev folks.
For iOS (ie. iPhone, iPod Touch, iPad)
I would recommend the following book: iPhone App School: XCode Programming for Total Beginners by David McMahon. Unfortunately, the book is only available for Amazon Kindle. I really liked this book as (a) it is cheap (only $4.99) and (b) just reading the first chapter gave me enough information to write a simple HelloWorld iOS app.
Apple also has a pretty good tutorial for building iOS apps here.
Again, I’m recommending a book by David McMahon, Learn Android Programming. It costs only $7.99 and again it’s only available for Amazon Kindle.
Google also has a pretty good tutorial for building Android apps here.